1. Field of the Invention
The present invention relates to an inverter-integrated electric compressor particularly suitable for use in a vehicle air conditioner and formed by installing an inverter inside an inverter box provided on the outer periphery of a housing, and to an assembly method therefor.
This application is based on Japanese Patent Application No. 2010-027733, the content of which is incorporated herein by reference.
2. Description of Related Art
In recent years, in addition to vehicles that run using internal combustion engines, vehicles that run by utilizing electric power, such as electric vehicles, hybrid vehicles, and fuel-cell-powered vehicles, are rapidly being developed and made commercially available. In many air conditioners for such vehicles that utilize electric power, electric compressors having motors that operate with electric power as a driving source are used as compressors for compressing and supplying a refrigerant.
Similarly, in some air conditioners for vehicles that run using internal combustion engines, compressors that are driven by the internal combustion engines via electromagnetic clutches are replaced by electric compressors so as to solve the problem of reduced drivability caused by the intermittency of the electromagnetic clutches.
A common example of an electric compressor of this type is a sealed electric compressor in which a compression mechanism and a motor are integrally built inside a housing. Furthermore, the sealed electric compressor is capable of supplying electric power input from a power source to the motor via an inverter and variably controlling the rotation speed of the compressor in accordance with the air-conditioning load.
In a proposed example of an electric compressor driven via an inverter in this manner, a control circuit board and the like that constitute the inverter are accommodated within an inverter box formed integrally with the outer periphery of the housing of the electric compressor so that the inverter is integrated with the electric compressor, and heat-generating electrical components, like power-controlling semiconductors, such as smoothing capacitors, that minimize the ripple of current supplied to the control circuit board and the like, and insulated gate bipolar transistors (IGBTs) are accommodated within the inverter box (for example, see Japanese Unexamined Patent Application, Publication No. 2003-153552 and the Publication of Japanese Patent No. 3786356).
In the integrated-type electric compressor discussed in Japanese Unexamined Patent Application, Publication No. 2003-153552, the heat-generating electrical components, such as IGBTs, mounted on the lower surface of the circuit control board of the inverter, with a gap therebetween, within the inverter box are in abutment with the bottom surface of the inverter box, that is, a heat-dissipating flat section (heat sink) thermally connected to the outer wall of the housing of the electric compressor, via a heat dissipation sheet composed of silicon rubber, as shown in FIG. 1 of the publication, whereby the heat of the electrical components is dissipated toward the housing.
In the integrated-type electric compressor discussed in the Publication of Japanese Patent No. 3786356, the heat-generating electrical components mounted on the lower surface of the circuit control board of the inverter, with a gap therebetween, within the inverter box are disposed directly in abutment with the bottom surface of the inverter box (housing), as shown in FIG. 2 of the publication, whereby the heat of the electrical components is dissipated toward the housing.
In order to maximize the heat dissipation effect for the heat-generating electrical components in such an inverter-integrated electric compressor, it is preferable that the electrical components be fastened to the bottom surface of the inverter box, that is, the heat-dissipating flat section of the housing, by using fastening members, such as screws, or be bonded thereto via an adhesive sheet or the like so that the electrical components and the heat dissipation surface are fixed and thermally connected to each other.
Because such an inverter-integrated electric compressor in general is directly attached to an engine of a vehicle, the inverter-integrated electric compressor constantly receives vibrations from the engine, vibrations from the vehicle body, rotational vibrations from the motor, and the like when the vehicle is running. The vibrations are also applied to the control circuit board of the inverter, causing the control circuit board to resonate mainly in the thickness direction thereof within the inverter box.
Therefore, with the configuration of the inverter-integrated electric compressor discussed in Japanese Unexamined Patent Application, Publication No. 2003-153552 and the Publication of Japanese Patent No. 3786356, relative displacement repeatedly occurs between the electrical components, mounted on the lower surface of the control circuit board with a gap therebetween and fixed to the bottom surface (i.e., the heat-dissipating flat section) of the inverter box by fastening or bonding, and the control circuit board vibrating in the thickness direction thereof. As a result, metal fatigue accumulates in lead terminals (pin terminals) that connect the electrical components to the control circuit board, possibly leading to deformation or breakage of the lead terminals with long-term use.
On the other hand, when assembling the inverter, the multiple electrical components are first arranged on the bottom surface (i.e., the heat-dissipating flat section) of the inverter box with their lead terminals oriented upward and are fastened thereto using screws or the like. Subsequently, the control circuit board is placed thereon from above, and the multiple lead terminals of the electrical components are inserted into lead-terminal through-holes in the control circuit board before the lead terminals are each soldered to the control circuit board. Therefore, an assembly procedure that involves a difficult and complicated positioning process is necessary, and moreover, the soldering process needs to be performed within the inverter box of the electric compressor. For this reason, the main body of the electric compressor needs to be conveyed in the assembly line of the inverter, resulting in extremely poor workability for assembling the inverter and its surrounding area.